Different kinds of organisms (arthropods, avians, mammals) are sensitive to pesticides. Pesticides are generally classified as herbicides, fungicides and insecticides. Pesticides interact with their nervous and enzymatic systems. Such toxicants may bind to binders (ion channels) located on the nerve cells, or to enzymes located around them and elsewhere. Pesticides also interact with various protective mechanisms, such as degrading enzymes and non-specific binders.
The brain and the nerve system of insects in general were the target for insecticides since their early development (1940s) for pest control in agriculture and human health. Pesticides that target the insect brain as the site of action usually display rapid action and require low dosage for good control.
Since the early 1970s, attempts have been made to use in vitro brain preparation to study the mode of action of pesticides. Only limited studies were reported on using this method for monitoring pesticides. Lack of stability and sensitivity as compared with the traditional gas chromatography (GC) or mass spectrometry made this early attempt useless. The use of color reaction requires high enzyme and substrate concentration to monitor brain preparation activity and the results were insensitive assays. The enzymes used were taken through laborious purifications, and it was found that only a limited spectrum of pesticides could be detected. Apparently, the source and the purified preparation were of limited sensitivity and for only a few pesticides which made it unsuitable as a monitoring and screening assay.
In recent years, bioluminescence or chemiluminescence has been used to detect extremely small quantities of material. Assays using these signals have been developed to measure substrates, such as ATP or NADH, and enzymes, such as alkaline phosphatase. Advantages to using bioluminescence as an assay system is the sensitivity of the reaction and the speed in which that reaction can be measured. For example, the bioluminescence reaction with the enzyme luciferase catalyzes the reaction between luciferin and ATP to produce light in milliseconds.
It is desirable to test for the concentration of pesticides in various materials, such as soil and water for health and safety purposes. In particular, it is desirable to provide an effective test kit and method to determine the concentration level of organophosphate and carbamate pesticides at low levels, such as below 50 ppb and even as low as 5 ppb. Specific organophosphate insecticides may be tested employing antibodies, but these have limited use as broad spectrum screening methods. Herbicides may be tested on a specific basis by chromogenic enzyme-based test methods, but such tests do not provide accurate results at low concentration levels and are susceptible to color interpretation.
Therefore, a new, accurate, effective test kit and method for the determination of pesticides, such as organophosphate and carbamate pesticides, are desirable.